1. Field of the Invention
The present invention relates to a method of applying conditions regarding a trapping process to be effected on a boundary region between two adjacent colors in an image on a printed material, and more particularly to a method of applying trapping conditions which is preferably applicable to a trapping process on an electronic editing apparatus for generating separation plates assembled from individual original images according to a computer process using an image display device.
2. Description of the Related Art
Generally, there is known a method of generating a printed material with an image on a print sheet according to a multicolor printing process using a plurality of printing plates which correspond respectively to a plurality of primaries, e.g., C (cyan), M (magenta), Y (yellow), and K (black).
Images on printed materials generated according to the multicolor printing process contain a boundary region between two adjacent colors. In the color-dividing boundary region, a blank gap may occasionally be produced due to a positional misalignment between a plurality of printing plates, a shrinkage or elongation of the print sheet, or other deficiencies.
It has heretofore been customary to carry out a trapping process for filling such a gap in a color-dividing boundary region by enlarging a figure in a background color in the color-dividing boundary region, or enlarging a figure in a foreground color in the color-dividing boundary region, or generating a fine line with a color including color elements of the two adjacent colors and placing the fine line along the color-dividing boundary region.
Each of the enlarged area of the figure and the fine line is referred to as a trap width. Recently, there has been available a trapping area generating program which can be executed on an image processing apparatus by a computer process for determining trapping parameter including those trap widths.
Trapping parameters are parameters, including the trap widths, used in the trapping process for determining which figure in the background or foreground color is to be enlarged (usually, the figure in a bright color is to be enlarged), and determining at least what difference between the equivalent neutral densities of the two adjacent colors is to be present before the trapping process is to be performed.
On the image processing apparatus in which the trapping area generating program is installed, the user uses an input device such as a mouse to specify an area where trap widths are to be generated (hereinafter referred to as “trapping area”) in an image on a page displayed on an image display device, as a rectangular frame or a free figure frame.
The image on the page displayed on the image display device includes all objects that constitute the page, i.e., a continuous gradation image such as a photograph captured by a scanner or a digital still camera, characters and figures entered on an electronic editing apparatus, pagination, etc.
According to the trapping area generating program, suitable trap widths are generated depending on the equivalent neutral densities of two adjacent colors in the color-dividing boundary region between the two adjacent colors in a specified trapping area.
For effecting a trapping process on a printed material having a plurality of pages, i.e., a book or the like, it is necessary to establish trapping conditions including trapping parameters and a trapping area for images on each page (also referred to as “objects to be trapped” or “editing materials”).
A task for establishing trapping conditions to indicate on which part of an image a trapping process is to be performed is a time-consuming process which needs to be carried out by an operator with professional knowledge.
Conventionally, it is necessary to establish trapping conditions for images on all pages of a printed material for each of the pages, and a process of establishing such trapping conditions is considerably time-consuming.
Particularly, header, footer, and logotype which serve as images on pages are present on all the pages. It is therefore a highly labor-intensive work to establish trapping conditions for these images on each of all the pages.